In many commercial as well as experimental processing operations, it is necessary to join together two members by a sealing means which prevents the escape of liquids, gases or vapors under pressure through the joint. In addition to withstanding high pressures, the joint must often be able to withstand relatively high temperatures. The formation of joint structures suitable for such conditions is compounded by a need to have such joints periodically opened and resealed. Accordingly, to completely satisfy the requirements, the joint structure must not only be able to prevent leakage under the high pressure, and perhaps high temperature, to which it is subjected but must also be one which can be opened and closed by suitable means.
Joint structures of different types are presently used in processing vessels which employ high pressures and temperatures. Such vessels generally contain a walled body having an opening which is closed by a head, cover or closure. The opening in the vessel normally has a rim or flange structure which mates or nests with an opposing face on the head or cover. Since it is often essential that there be periodic access to the vessel interior, the head or cover is releasably secured to the vessel. To prevent leakage at the interface between the cover and the vessel, various types of gaskets and sealing means are used.